Variation in mitochondrial translation products associated with male-sterile cytoplasms in maize

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Abstract
Mitochondria were isolated under sterile conditions from maize [Zea mays] lines with normal cytoplasm and with T, C and S sources of cytoplasmic male sterility. Protein synthesis by these mitochondria was dependent upon the presence of ADP and an oxidizable substrate or an energy generating system and displayed characteristic sensitivity towards inhibitors of protein synthesis. Approximately 20 polypeptides were detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis of the [35S]methionine-labeled mitochondrial translation products. Mitochondria from the T and C cytoplasms were characterized by the synthesis of a single additional or variant polypeptide. These observations are discussed with reference to the possible mechanisms of male sterility and the susceptibility of plants with T cytoplasm to Helminthosporium maydis, race T. Our results also suggest a potentially rapid method of classifying sources of cytoplasmic male sterility that could be used in conjunction with existing methods, which depend on patterns of fertility restoration after an extended breeding program.